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ACC-0008 • Don't Fear Halftones

Don’t fear the halftone, it is possibly the single greatest invention in the print industry. Professional printers understand, control, and embrace the use of halftones.

 

The invention of the halftone sent positive shock waves through the print industry, enhancing it forever. Before the halftone, printing was very limited. Chromolithography which was basically “indexing” was the popular method. Images required very large amounts of separations (generally 16 colors for more), the style of printing was very limited. Look at prints produced between the late 1800s and early 1900s (reference Currier and Ives).

 

 

Fearing halftones will limit your business, professional enjoyment, and possibilities. Sometimes, clients want designs beyond basic black outline and solid spot color fills. It’s simple to create a tint, gradient or blend in an any modern art file. It’s extremely easy to separate them too from all main stream software such as Adobe Illustrator or Corel Draw. Spot Process Sep Studio is a shining example of a powerful, but easy to manage halftone separation software. It delivers a full set of tonal image separations as solid and halftone spot colors. AccuRIP takes all the worry out of achieving properly dense halftones on film.

 

Why the fear? It could be a lack of confidence in screen making. Screen printers worry about their ability to expose (capture) the smaller halftones. That is a concern to all screen printers, but it should not be a fear or a reason to avoid their use. Here’s how you too can learn to understand, manage, and enjoy the use of halftones. There are proven steps and great solutions to eliminate the fear. What should you do?

 

Step by step:

 

Step One:

Set your RIP software to produce an industry standard 45 line screen halftone at an angle of 22.5 degrees. Print a halftone file to film. You can even use AccuRIP’s halftone test print (Open AccuRIP, from the File menu choose Test print).

 

Step Two:

Prepare a screen. The mesh count should be 5x the selected halftone line screen (eg. 45 line screen x 5 = 225. Select the equal or next higher mesh count number such as 230, never a lower number. Higher avoids moire.). Emulsion and dry the screen with with “print side down” helping the emulsion settle to the print side of the mesh. This is a critical step. Screens must be dried in the same position they are used on press. Any other position will hurt the exposure process, creating issues holding the halftones. Use yellow mesh over white. White causes a lot of light reflection and refraction.

 

Step Three:

Expose the screen at the manufacturers recommended settings based on your exposure unit style and intensity. Too much time and light will over expose the screen, causing you to lose the lower end halftone tones.

 

Step Four:

Wash out, and dry the screen. Use a gentile force when washing out. Don’t use the same pressure used to “reclaim a screen”. Emulsion protected from the light by the film is still water soluble. No need to apply great force. If you do need great force then you probably over exposed the screen. Try agin using less time and light. A medium mild mist should do the job.

 

Step Five:

Using the single color screen print black ink to a white garment.

 

If the results are less than quality determine what part of the process shows the breakdown in quality. For example, did the emulsion not harden properly and too much washed away down the drain along with detail (emulsion colored water)? That would be a sign of under exposing your screen because of not enough time or a weak light source.

 

The emulsion exposed rock hard, but you lost a lot of lower to mid range halftones. Your exposure unit is very strong, you exposed the screen too long or your films are not dense enough. We will cover how to determine proper film density in a future post.

 

Your software, emulsion, and exposure unit manufacturers provide info and support for the use of their products. Reach out for help. Generally, printers are surprised to discover that their fears can easily be over come and that the causes of the issues were generally in the screen making department. Accomplishing this test will help you tighten down all your pre-press systems and workflows improving your business and end result which can only make you a better printer and business.

Any document, pdf or link mentioned in this article can be located in the Resources.

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